CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from United Kingdom Patent Application No. 15 05 590.8, filed 31 March 2015, the entire disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to apparatus and a method for uniformly coating a surface, and in particular to uniformly coating the deck surface of an aircraft carrier.

2. Description of the Related Art

The deck of an aircraft carrier needs to be protected in order to prevent immediate destruction of the deck each time an aircraft lands on the deck of the carrier. It is known to protect the deck of an aircraft carrier by painting the deck. However, the conditions and environmental elements associated with a jet landing on the deck are such that a deck needs to be re-painted at least every three years. It is also known to apply a surface coating to the deck of an aircraft carrier for protection, using industrial robotic machines. However, existing industrial robotic machines exemplified by thermal spray machines have many disadvantages which include an inability to manoeuvre into awkward spaces on the deck and an inability to deliver a uniform level of coating onto the deck regardless of undulations on the surface of the deck and deck furniture and fittings.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided apparatus for uniformly coating a surface, comprising: a servomechanism having first, second and third longitudinal axes; a process unit configured for coating a surface, said process unit being mounted on one of said longitudinal axes; and a sensor configured to detect surface variations a predetermined distance ahead of said process unit and to transmit data to said process unit; wherein said process unit is configured to produce a signal in response to receipt of said data to alter the level of a coating directed onto the surface.

According to a second aspect of the present invention, there is provided a method of uniformly coating a surface, comprising the steps of: detecting a surface variation using a sensor to produce data; transmitting said data to a process unit, said process unit producing a signal in response to receipt of said data; and altering the level of a coating directed onto a surface in response to said signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows an aircraft carrier with jet onboard;

Figure 2 shows a perspective view of the embodied apparatus;

Figure 3 shows the three axis servo machine of the embodied apparatus;

Figure 4 shows an element of the process unit in one embodiment;

Figure 5A shows a perspective view of thermal arc sprays and Figure 5B shows a cross section of thermal arc sprays;

Figure 6 illustrates the sensor in the embodied apparatus;

Figure 7 shows a cross-section of a plan view of the embodied apparatus;

Figure 8 illustrates the extraction system in the embodied apparatus; Figure 9 illustrates the process control system in the embodied apparatus;

Figure 10 illustrates the remote control unit embodied in the present invention;

Figure 11 is a schematic illustrating the feathering pattern achieved by the present invention;

Figure 12 is a schematic to show the feedback from the sensor to the process unit to enable the coating process to be altered; and

Figure 13 sets out the method embodied in the present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Figure 1

An aircraft carrier serves as a seagoing airbase and can both receive and deploy large numbers of fighter planes, helicopters and other types of aircraft. The deck of an aircraft carrier is the surface of the vessel which acts as a runway from which aircraft take-off and land. Figure 1 shows jet 101 landing on deck 102 of aircraft carrier 103. Figure 1 also shows jet 104 taking off from deck 102.

In the illustrated embodiment, jet 101 and jet 104 are short take-off and vertical landing aircraft (STOVL aircraft). STOVL aircraft are a fixed-wing aircraft that can take off from a short runway, for example, on board an aircraft carrier such as carrier 103, and land vertically.

The deck of an aircraft carrier needs to be protected in order to prevent immediate destruction of the deck each time an aircraft lands on the carrier. In particular, the extreme temperatures associated with the thrust vectoring utilised by a STOVL jet landing on the deck of an aircraft carrier can cause immediate destruction of the deck.

A first example of a known method for protecting the deck is painting. However, the aforementioned thrust vectoring and temperature of a jet landing on the deck are such that the lifespan of a painted deck is only three years or less. The deck therefore needs to be painted on a frequent basis which is costly, time-consuming and usually requires the aircraft carrier to be in dry dock, thereby reducing its sea-going time.

A second example of a known method for protecting a surface is to use a surface coating technology and apply it onto the deck using a metal spray system. A known coating technology is the metal spray coating and spray metalizing system developed by Thermion® which deploys ceramically impregnated wire. These existing industrial robotic thermal spray machines have many disadvantages which include an inability to be autonomously driven, an inability to manoeuvre into awkward spaces on the deck and an inability to uniformly coat the deck surface regardless of undulations on the surface of the deck and deck furniture and fittings.

Figure 2

Figure 2 shows a perspective view of the embodied apparatus 201. The apparatus of the present invention overcomes the aforementioned disadvantages of the prior art and in particular, can be autonomously driven, can manoeuvre into awkward spaces on the deck and can uniformly coat the deck surface regardless of undulations and deck furniture and fittings. In addition, the present invention can allow the coating to be delivered to the surface whilst the carrier is at sea, advantageously reducing the amount of downtime of the aircraft carrier.

The present invention relates to an apparatus for uniformly coating a surface. The term "coating" is used throughout as both a verb and a noun. When used as a verb, the term "coating" is intended to mean delivering a variety of mediums or substances to a surface (such as those mediums or substances set out directly following this sentence). When used as a noun, the term "coating" is intended to mean the coatings themselves, which may include a thermal metal spray coating as illustrated within the embodied invention, paint, varnish, infra-red radiation, compressed air, water, chemical vapour depositions, physical vapour depositions, any chemical or electrochemical coating, and other mediums or substances required to prepare a surface, coat a surface and seal or cure a surface. When used as a noun, the term "coating" is therefore used in a general sense and may include any substance in gaseous, liquid or partially solid form. The apparatus of the present invention comprises a servomechanism or three axis servo machine 202 having three longitudinal axes corresponding to conventional x, y and z directions. Arrows 203, 204 and

205 are used respectively in Figure 2 to represent the x, y and z longitudinal axes. The three axis servomechanism is adjustable in a left-right movement along the x axis (203), a forward-backward movement along the y axis (204) and an up-down movement along the z axis (205).

In the embodiment, a process unit 206 is mounted along the z axis (205) a distance away from the servo machine 202. Process unit 206 is configured to deliver a coating on to the deck of the aircraft carrier. The process unit can alter the level of coating directed onto the surface in order to ensure a uniform coating of the surface by a number of mechanisms. These mechanisms include altering the position along the z axis (205), altering the amount of coating sprayed from the process unit 206, altering the speed along the y axis (204) and/or tilting the process unit 206. Additional mechanisms which ensure a uniform coating of the surface lie within the scope of the present invention. In the illustrated embodiment, process unit

206 comprises three spray gun heads. However, in alternative embodiments, the process unit may be changed to, for example, a blast head which would be suitable for the process of surface preparation. Alternatively, the process unit may be an ultra-high pressure water head for jetting water onto the surface or a paint head suitable for painting the surface. The paint could be, for example, an inorganic paint system which not only applies colour to the deck, but also seals the porosity of the deck and prevents it from attracting water. Merely as a further example, the spray gun head of the process unit may be changed to an infra-red curing head for curing the surface. The apparatus of the present irrvention can thus be used for not only delivering a thermal metal spray coating to a surface, but also a range of substances, all of which coat the surface, for example, water or paint. The apparatus could therefore be used in a wide range of settings including oil rigs or helidecks.

In a further alternative embodiment, there could be a combination of different guns attached to the process unit, to allow surface preparation and curing to take place without the need to change the attachments on the process unit. For example, there may be one blast gun for surface preparation and one gun for coating the surface with a thermal metal spray. As a further example, there may be one gun for coating the surface with a thermal metal spray and one or more infra-red radiation units for curing the surface. This enables the speed of the entire process of protecting the deck (including surface preparation, adding protective layer such as thermal metal spray and curing) to be significantly increased.

The apparatus of the present invention operates on a separate heavy engineered steel frame 207 which is mounted underneath the frame of the three axis servo system. The separate heavy engineered steel frame 207 moves the whole apparatus around the deck of the aircraft carrier, enables the apparatus to manoeuvre into awkward spaces on the deck and enables autonomy of the apparatus. Frame 207 needs to be kept as slim as possible at one edge to enable the apparatus to move as close as possible to the edge of the deck and to the edge of deck furniture and fittings.

On each of the four corners of frame 207, there is mounted a motor gearbox (not herein shown) which drives a pneumatic tyre wheel arrangement 208. There are an additional two motor gearboxes for the steering mechanism, one at the centre front of the apparatus and one at the centre back of the apparatus (cannot be seen in Figure 2).

The motor gearboxes are mounted on plates which allow tyre wheels 208 to be automatically steered independently front to back and a linkage between the plates aids the control of tyre wheels 208. Tyre wheels 208 can be steered 90° (ninety degrees) left or right, both on the front and back of the apparatus, so that the apparatus can be moved into smaller places on the deck. The apparatus needs to be steered as efficiently and accurately as possible.

The base of the heavy steel-engineered frame 207 has a floored gantry 209 with personnel access. The gantry 209 also comprises an onboard industrial personal computer (IPC) for control of the process. The IPC includes a simple touch screen which is used to finely control the variables of the process.

The three axis servo machine 202 and process unit 206 are contained within a safety frame 210 for man life safety reasons and also to help minimise oxidation of the process, which is undesired. Safety frame 210 is typically transparent to allow for observation of the process unit and typically fabricated from a tough bullet-proof plastics material, such as a polycarbonate. However, the skilled person would understand that alternative materials may also be fit for this purpose.

Safety frame 210 (or safety guard) is an important element of the embodied apparatus 201 because a lot of dust, particulates and fumes are created during the operation of process unit 206, regardless of the nature of the coating being applied to the surface. Frame 210 surrounds three axis servo machine 202 and process unit 206. Frame 210 ensures that all of the dust, particulates and fumes created by the process can be controlled. An external dust extraction system may be deployed to draw the dust out, as illustrated in Figure 8. There thus may be connections to one or more external extraction units.

It is extremely advantageous to have the option to use an integral safety frame 210 to avoid the need to move safety frame 210 separately each time apparatus 201 moves. In prior art systems, the safety guard is always a separate component and needs to be moved each time the apparatus is moved. The safety frame 210 keeps the deck clean, because if dust is created ahead of where the apparatus is to move to, the deck will have to be cleaned again before it can be sprayed.

As mentioned above, safety frame 210 can also help reduce oxidation of the process. Thousands of tiny holes are created during the process as the coating impacts the surface. When the coating is a thermal metal spray, many of these tiny holes are filled by the molten metal and thus form part of the coating, but some are not filled. If there is moisture ingress into an area, small patches of oxidation may form. The presence of safety frame 210 can help to minimise oxidation.

The embodied apparatus 201 has a frame of three metres (3m) by four metres (4m), giving a twelve metre squared (12m ² ) work envelope. However, it is within the scope of the present invention that the apparatus could be scaled up in size to have a larger frame of, for example, ten metres (10m) by ten metres (10m). Existing industrial robotic thermal spray machines, such as those available from Thermion®, only have a frame of three metres (3m) by two metres (2m) and consequently a smaller work envelope. Existing industrial robotic thermal spray machines are not self driven and therefore once a six metre squared (6m ² ) envelope has been sprayed, the robotic machine must be lifted using a crane to a new area. In contrast, the proposed apparatus is automatically self-driven. Production rates of the present proposal are therefore much enhanced over existing solutions.

Figure 3

Figure 3 shows the three axis servo machine 202 of the embodied apparatus. The apparatus of the present invention comprises a three axis servo machine or servomechanism 202 having x, y and z longitudinal axes. Arrows 203, 204 and 205 are used respectively in Figure 3 to represent the x, y and z longitudinal axes. The x axis (203) is left-right movement, the y axis (204) is forward-backward movement and the z axis (205) is up-down movement. This naming of the direction of movement of the three axes will be used consistently.

Mounted onto the z axis (205) is a head 301 designed to take a payload of approximately ninety kilograms (90 kg), although it is within the scope of the invention that this payload can be increased. The process unit (not herein shown but shown in Figure 2 as 206) which is configured to deliver a coating to the surface attaches to head 301. Figure 4

An element of the process unit of an embodiment of the present invention is illustrated in Figure 4.

In the illustrated embodiment, the element of the process unit is a thermal arc spray gun capable of delivering a thermal metal spray coating to a surface. As discussed in connection with Figure 5, the thermal arc spray unit comprises three spray guns mounted onto the head (301 in Figure 3) of the z axis and forming an integral part of the apparatus. There is scope within the present invention for the process unit to comprise an alternative number of heads.

In the illustrated embodiment, the coating itself is a thermal metal spray. The coating is a heated metal which is sprayed onto a surface using twin wire arc spray equipment, one wire for a thermal aluminium spray and one wire for a thermal aluminium/titanium spray (an Al-A/Ti mixture). The coating has anti-corrosion, heat-resistance and anti-slip properties and may be used in a wide range of environments and climatic conditions. The coating has been vigorously assessed including tests in blast chambers, salt spray tanks and having different gases fired at it. The estimated lifespan is 25 years under challenging conditions. However, as discussed above, the coating may be any substance in any form for preparing a surface, coating a surface and curing or sealing a surface.

Figure 4 shows a single spray gun 401 with pistol component 402 for delivering thermal metal spray coating. Tube 403 delivers compressed air required by the spray gun for delivery of the coating and tubes 404 provide positive and negative electrical connections in order to make the arc spray. Knobs 405 are for adjustment of the drive roller wire tension of the two wires as described above to alter the spray levels.

The automation and the way in which the three axes of the three axis servo machine are controlled allow a surface to be uniformly coated. For example, as discussed in connection with Figure 6, control of the z axis (up and down movement) is required to compensate for undulations on the surface of the deck.

Figure 5 A and Figure 5B

In Figure 5A, a process unit, and in particular, a thermal arc spray unit comprising three guns 501 is illustrated.

The three arc spray guns 501 are mounted on plate 502 on a work head 503. There are two wires 504 and 505 leading from each arc spray gun. The movement of plate 502 can be altered, which affects the orientation of the arc spray guns. The movement of plate 502 can be altered by tilting in any direction. Such fine movements are useful in ensuring that a uniform level of coating is produced, regardless of undulations on the surface of the deck or deck furniture and fixtures. In addition, the rates and physical position of each of the three spray guns 501 can be altered individually to again ensure that a uniform level of coating is produced.

Furthermore, plate 502 may comprise slots into which spray guns 501 are inserted. Guns 501 are capable of sliding within these slots. It is therefore possible to alter the distance between individual spray guns 501 which can be useful when ensuring a uniform coating is delivered to extreme edges or corners of surface or when encountering an object on the surface of the deck. In an embodiment of the invention, it is possible to automate the movement of the spray guns 501 on plate 502 (automatic gun positioning).

In Figure 5B, a cross-section of the process unit is illustrated. An analogue control (not shown) is used to vary the feed rates on the three arc spray guns 501. The molten metal is sprayed in an electrical arc 506 downwards and hits the surface at a high velocity, bonding itself to the substrate. By using the Al-A/Ti mixture, a build-up of coating is created on the surface. The level of the coating depends on the feed rate of the wires 504 and 505 to create the arc 502 against the speed of the movement of the y axis. Therefore, if the feed rate is one hundred percent (100%), the deposition rate is one hundred percent (100%). To change the thickness level of the coating that is applied, either the percentage of the feed rate of the arc spray unit is altered or the speed of movement of the y axis is altered. In the embodied invention, both of these variables can be manipulated for precise control. It is essential that the surface coated is of a high quality in order to meet the quality standards set out by the National Aerospace and Defence Contractors Accreditation Program (Nadcap).

Figure 6

The apparatus of the present invention comprises a sensor which is configured for detecting surface variations and undulations a predetermined distance ahead of the process unit 206. In Figure 6, there are two laser sensors 601 positioned on the right and left hand side of the z-axis and are used to measure one metre (1m) in front of the process unit. Laser sensor 601 can take into account the deviations in the height of the deck and signal to the z axis to move accordingly. This is necessary to ensure that the level of coating is maintained over the deck, regardless of the undulations or deck furniture 602. It is an essential element of the invention that the deck undulations are detected and the process altered accordingly automatically.

In the illustrated embodiment, laser sensor 601 is used but it is within the scope of the present invention that any type of sensor may be used, for example radio-frequency sensors, ultrasonic sensors or short-range radar sensors. These examples of types of sensor may be used for detecting undulations on the deck. Machine vision techniques using video cameras and/or vision sensors may also be used for detecting deck furniture or fittings. Further, any such sensor may be able to sense any predetermined distance ahead of the process unit, from a few centimetres to a few metres.

In the illustrated embodiment, there are two laser sensors 601 positioned on the left and right hand sides of the z axis.

Sensor 601 detects surface variations and feeds back data to process unit 206. In response to this data, process unit 206 produces a signal and consequently alters the level of coating directed onto the surface. The ability of process unit 206 to compensate for small changes and variations in the surface is a unique part of the present invention.

Therefore, if sensor 601 detects a particular undulation such as a raised bump that requires a lower level of coating to be delivered to the surface, in order to maintain a uniform level of coating, it is possible to do one or more of a number of things including: i) reduce the amount of feed spray; ii) increase the speed along the y axis; iii) adjust the position along the z axis to move the servomechanism further above the surface; and iv) tilt the plate onto which the process unit is fixed.

Conversely, if sensor 601 detects a particular undulation such as an indentation that requires a higher level of coating to be delivered to the surface, in order to maintain a uniform level of coating, it is possible to do one or more of a number of things including: i) increase the amount of feed spray; ii) decrease the speed along the y axis; iii) adjust the position along the z axis to move the apparatus closer to the surface; and iv) tilt the plate onto which the process unit is fixed.

The process of controlling the presently claimed apparatus also enables a process of feathering to occur, as explained in Figure 10. It is necessary to maintain certain quality standards as set out by the National Aerospace and Defence Contractors Accreditation Program (Nadcap), a global cooperative accreditation program for aerospace engineering, defence and related industries.

In the illustrated embodiment, a further sensor 603 is installed on each of the four top corners of the apparatus in order to aid with the positioning and alignment of the apparatus itself.

In an alternative embodiment, there may be installed an additional sensor (not herein shown) in order to detect the quality of the coating applied to the surface.

A further reason for making adjustments to the feed rate may be to try to minimise excessive porosity, which is a moisture trap, and consequently the possibility of undesirable oxidation. Figure 7

Figure 7 shows a cross-section of a plan view of the separate heavy engineered steel frame which is mounted underneath the frame of the servo system (not shown in Figure 7). This heavy engineered steel frame 201 moves the whole apparatus around the deck of the aircraft carrier (or alternative surface) and allows automated movement of the apparatus. The base of the heavy steel-engineered frame 201 includes floored gantry 209. Floored gantry 209 has personnel access in order to operate industrial personal computer (IPC) 701 whenever required. In the illustrated embodiment, gantry 209 is positioned at the side of frame 201.

On each corner of frame 201, there is mounted a motor gearbox 702 which drives a pneumatic tyre wheel arrangement 703. In the illustrated embodiment, there are also an additional two motor gearboxes 702, one at each side of the apparatus, for the steering mechanism. In alternative embodiments, there may be any number of motor gearboxes with their associated pneumatic tyre wheel arrangements. Motor gearboxes 702 are mounted on plates 704, allowing the tyre wheels 703 to be automatically steered independently front to back. Linkage 705 between plates 704 aids in the control of the movement of the frame 201. Wheels 703 can be steered ninety (90) degrees left or right, both on the front and back of the apparatus, so that the apparatus can be moved into smaller places on the deck.

Figure 8

The three axis servo machine and process unit of the embodied invention are contained within a safety guard/frame for man life reasons and also to help minimise undesirable oxidation of the process. As illustrated in Figure 8, three axis servo machine 202 and process unit 206 are contained within safety frame 210, which controls all of the dust, particulates and fumes created by the process. Furthermore, the embodied apparatus has a connection 801 to an external extraction unit 802. The embodied apparatus is entirely autonomous apart from connection 801 and cables to an electrical power supply (connected to apparatus at a rapid release connection point), not herein shown.

Figure 9

Figure 9 illustrates industrial personal computer (IPC) 901 onboard gantry 209, which extends to the rear of the apparatus and allows personnel access. The IPC of the present invention uses Programmable Logic Controller (PLC) control equipment 902 for control of the coating processes of the process unit. The PLC is connected with IPC 901 to facilitate the human-machine interface. IPC 901 includes a touch screen 903 which is used to finely control the variables of the process. The process is repeatable so that consistent results are achieved.

Remote access will also be deployed via 3G (the third generation mobile network or service conforming to IMT-2000 standards) or wireless technology to view software onboard the apparatus and production data. Remote access will encompass means to restrict access to particular elements of software. Gantry 209 may also include a closed circuit television (CCTV) for security purposes (not herein shown). In addition, gantry 209 may include a biometric scanner onboard to control access to the IPC. For example, certain individuals may only be given access to start and stop movement of the process unit whilst other individuals may be given full control of the process. Additional access and security controls onboard the apparatus as would be anticipated by a person skilled in the art are within the scope of the invention.

Figure 10

The embodied invention may comprise remote control to the apparatus, deploying a bespoke pendant, as illustrated in Figure 10. Remote control unit 1001 will be used predominantly for control of movement of the whole apparatus. An operator can use their line of sight to control movement using remote control. However, software also includes standard stages to move the apparatus in a straight line and around pieces of furniture. In order to enhance the degree of accuracy of the steering and positioning of the apparatus, a laser sensor (in addition to sensor 603) may be used. Figure 11

When using existing industrial robotic thermal spray machines, raised layers of coating may be formed, especially when the apparatus approaches the edges of the deck and pieces of deck furniture. These raised layers are problematic and undesirable because a uniform level of coating is needed for optimal functioning of the coating in its anti-corrosion, heat-resistance and anti-slip properties.

However, the apparatus of the present invention allows for feathering in and out when the apparatus approaches the edges of the deck and pieces of deck furniture so that raised layers of coating are not formed. An alternative term for feathering may be smoothing-off or rounding-off. It is necessary to start feathering when the apparatus approaches extremities of the deck, deck furniture or fittings and also when layers of coating may slightly overlap.

Figure 11A illustrates a problematic raised layer 1101 produced by the industrial robotic machines of the prior art. The layers of coating overlap, and because there is no feathering, a raised layer 1101 is formed.

Figure 11 B illustrates the uniform layer 1102 produced by the embodied apparatus as a result of feathering. In contrast to Figure 11 A, it is clear that there is no raised layer. As the apparatus of the present invention moves forward along the y axis, a strip of one hundred and twenty millimetres (120mm) is covered. This is not a fixed dimension, and may vary in size in alternative embodiments. This is because in the embodied invention, the diameter of the arc spray from one gun is 120mm. However, in alternative embodiments, the diameter of the arc spray gun may vary.

The one hundred and twenty millimetre (120mm) diameter of the arc spray from one gun is represented by line 1103. During the feathering process, the coating sprayed from the gun is reduced in level across the diameter 1103. The spraying pattern is effected by varying any of the parameters. Any of the mechanisms as exemplified herein may be deployed to reduce the level of coating to allow the feathering to take place. These mechanisms may include any of those as set out in the description accompanying Figure 12. Any one or more of the mechanisms may be deployed to overcome the specific details associated with a particular edge, corner or piece of deck furniture.

Figure 1C shows a typical layer 1104 produced by the process unit of the present invention. In reality, the layer is not entirely smooth, but has a surface coating with prescribed roughness, which advantageously increases the anti-slip properties of the coating.

Figure 12

Figure 12 shows a schematic of the sensing process embodied in the present invention. Sensor 1201 is positioned on the left and right hand sides of the z axis, but may be positioned at an alternative site. In the embodied invention, sensor 1201 is a laser sensor, but in alternative embodiments, may be a different type of sensor such as radio-frequency, ultrasonic or short-range radar. In the embodied invention, sensor 1201 detects the predetermined distance of one metre ahead of the process unit, but in alternative embodiments, may detect different distances ahead of the process unit.

Sensor 1201 detects surface variations 1202 and produces data relating to these surface variations 1202. This data is fed back to a process unit 203. A signal is produced by process unit 1203 in response to said data and the level of coating directed onto the surface in response to the signal is altered.

The level of coating directed onto the surface in response to the signal may be altered by a number of mechanisms. The following does not represent an exhaustive list, but merely examples for the ways in which the rates of the guns and their physical position may be changed, in order to alter the level of coating.

The process unit is fixed to the head of the z axis. The position of the z axis may be adjusted (1204), so that if more coating is required, for example, because the sensor has detected an indentation, the process unit is brought closer to the surface. If less coating is required, for example, because the sensor has detected a bump, the process unit is moved further away from the surface.

The amount of coating released from the process unit may be increased or decreased (1205).

The guns which make up the process unit are fixed to a plate. This plate can be tilted (1206) in any angle and to any degree to allow for uniform covering when the apparatus reaches extremities of the deck.

The speed of the y axis may be altered (1207). If the sensor 1201 detects an indentation, such that more coating is required, the speed of the y axis can be decreased so as to allow more time for coating to fill in the indentation. Conversely, if the sensor 1201 detects a raised bump, such that less coating is required, the speed of the y axis can be increased so as to ensure that less coating fills in the indentation.

The guns are positioned into slots in the plate and can easily be moved along within the slot, with the result that there need not be an equal distance between guns. Having, for example, two guns closer together to each other and one gun further away may be advantageous when the apparatus encounters deck furniture or fittings. In an embodiment, it can also be possible to automate the movement of the guns on the plate, known as "auto gun positioning".

Furthermore, one of the three, or two of the three spray guns can be sprayed off, e.g. if an object on the deck is detected.

Further still, there may be a different percentage of spray released from different guns, for example one gun may be spraying at 100%, whilst the other two guns may only be spraying at 50%.

It is to be appreciated that any number and any combination of the above mechanisms may be deployed to ensure a uniform covering of a surface regardless of undulations, deck furniture and fittings.

Figure 13

The method for uniformly coating a surface, embodied in the present invention, is set out in Figure 13. At step 1301 , surface variations are detected using a sensor and data is produced. At step 1302, this data is fed back to a process unit. At step 1303, the level of coating directed onto surface is altered in response to a signal produced by process unit in response to the data. The level of coating directed onto surface may be altered be any mechanism, including those set out in Figure 12 and the accompanying Figure 12 description.